The present invention relates to a semiconductor integrated circuit which can be mounted in a motor drive controller for driving a motor to move a magnetic head of a hard disk drive unit, and an operating method for the same. Particularly, the present invention relates to technology which is effective in performing a calibration operation for velocity detection of the motor, without using the digital correcting by an external CPU of the semiconductor integrated circuit.
In a hard disk drive unit (HDD), a magnetic disk is rotated at high velocity by a spindle motor, a magnetic head for read and write is floated at a close distance on a medium surface of the rotating magnetic disk, and the magnetic head is moved in the diameter direction of the magnetic disk by a voice coil motor, thereby the read and write of information of the magnetic disk are performed.
In the hard disk drive unit (HDD), a loading/unloading system is adopted in which, when the write and read of data is not performed, the magnetic head is retracted to a ramp mechanism provided outside the outer circumference of the magnetic disk and rests there. By a loading operation according to a command from a host, the magnetic head is moved to the disk medium surface from the retracted position of the ramp mechanism, and a read/write operation is performed. After the completion of the read/write operation, by an unloading operation according to a command from the host, the magnetic head is moved from a disk medium surface to the retracted position of the ramp mechanism, on the contrary.
On the other hand, with the increasing advancement of high recording density of a hard disk drive unit, the flying height of a magnetic head over the disk medium surface becomes small, and improvement in the accuracy of the velocity control at the time of loading of the magnetic head is required. The velocity at the time of loading of a magnetic head is moving velocity of the magnetic head from the retracted position of the ramp mechanism to a disk medium surface. The velocity at the time of loading of the magnetic head is conventionally controlled by detecting a back electromotive force generated in the voice coil motor at the time of the movement.
Patent Document 1 cited below describes that an inter-terminal voltage of a voice coil motor (VCM) and an inter-terminal voltage of a sensing resistor coupled in series with the voice coil motor are amplified by a two-stage negative feedback differential amplifier, thereby the back electromotive force of the voice coil motor is detected. Patent Document 1 also describes about a calibration operation which is performed in order to compensate an error involved in the detection value of the back electromotive force which arises from the change of the parasitic resistance of the VCM (VCM resistance) due to a temperature change. That is, when starting the loading control, in a zero state of the actual velocity of the VCM when the carriage is pressed against an outer circumference stopper, VCM velocity detection values detected from a VCM detection circuit are read when two steps of VCM current values are made to flow through the VCM, then, the relation between the VCM current value and the VCM velocity detection value is compensated by the software processing by a CPU. Furthermore, in performing the unload control, when a timer value has exceeded the prescribed time, the retracting operation is performed to retract the magnetic head to the inward direction of the magnetic disk, and the carriage is pressed against an inner circumference stopper. In the present state, two steps of the VCM current values are made to flowin a direction in which the driving force to the carriage acts toward the inner circumference, and the relation between the VCM current value and the VCM velocity detection value is compensated similarly by the software processing by the CPU.
(Patent Document 1) Published Japanese Unexamined Patent Application No. 2000-163901